Re: [RFC PATCH v2 2/8] tools/nolibc: Remove .global _start from the entry point code

[Nick Desaulniers <ndesaulniers@google.com>]

On Tue, Mar 22, 2022 at 11:24 AM Willy Tarreau <w@1wt.eu> wrote:
>
> What I particularly like is that I don't need a full toolchain, so if
> I can build a kernel with the bare-metal compilers from kernel.org then
> I know I can also build my initramfs that's packaged in it using the
> exact same compiler. This significantly simplifies the build process.

Neat; yeah that coincides a bit with my interest in having builds of
llvm on kernel.org; having/needing a libc is a PITA and building a
full cross toolchain is also more difficult than I think it needs to
be.  The libc will depend on kernel headers, for each target.  LLVM
currently has a WIP libc in its tree; I'm looking for something I can
statically link into the toolchain images (even LTO them into the
image).  Will probably pursue musl (if I ever get time for this,
though maybe a project for my summer intern...).

One thing I've been looking at is a utility called llvm-ifs [1]; it
can generate .so stubs from a textual description that can be more
easily read, diff'ed, and committed. These are much faster to build
and reduce the chain of build dependencies (when dynamically linking).
Last I checked it had issues with versioned symbols, and I'm not sure
if/what it does for headers, which are still needed.  Within Android,
libabigail is being used to dump+diff xml descriptions of parts of an
ABI, it looks like llvm-ifs might be useful for that as well.  Not
sure if it's interesting but thought I'd share.

[1] https://www.youtube.com/watch?v=_pIorUFavc8
-- 
Thanks,
~Nick Desaulniers